Today's society has a seemingly ever-growing desire for portable electronic devices that are more robust, lightweight and versatile. One growing area of consideration for such products is the development of devices in a flexible form factor that can operate without deterioration in performance. In order for flexible displays and photovoltaics to be commercially successful, they should be robust enough to survive for the necessary time and conditions required of the device.
Beyond flexibility, printability and functionality of the components, other important requirements lie in making thermally stable materials that are less susceptible to interaction with many environmental components, such as oxygen and moisture. Some of the most difficult performance metrics to meet are the requirements for low permeability to water and oxygen (10−6 g/m2/day for H2O and 10−5 g/m2/day for O2) and thermal stability (ideally up to 300° C.).
Substrates and barriers such as glass and metal provide excellent barriers to oxygen and moisture, but result in rigid devices that do not satisfy applications demanding flexible devices. On the other hand, plastic substrates and transparent flexible encapsulation barriers may be used, but these offer little protection to oxygen and water, resulting in devices that rapidly degrade.
A commercially available polyethylene naphthalate (PEN) film is only thermally stable up to about 200° C., and its permeability to oxygen and water is too high to meet the permeability requirements. Other commercially available flexible polyimide resin materials have very high thermal stabilities (about 350° C. to about 400° C.) but do not meet the permeability requirements.
Therefore, there remains a need for flexible barrier layer materials and flexible substrate layer materials that meet the required permeability parameters for oxygen and water, while also being compatible with high-temperature processing or integrated functionality.